There has been known a packaged electrode produced by packaging electrode between a pair of separators (Patent Literature 1). In this packaged electrode, the separators are joined together at least at four corners.
The separators are thin films, which are easily peeled off. Since batteries for electric vehicles or hybrid vehicles, in particular, are much larger than those for home appliances, handling thereof is difficult and the separators are likely to get wrinkled in addition to peel-off. For this reason, the separators are peeled off or get wrinkled when overlaid on both sides of the electrode. This complicates a joining operation to join the edges of the separators together. Therefore, the efficiency of producing packaged electrodes deteriorates, and in turn, the efficiency of producing an entire battery cannot be increased.